It is known to ventilate the roof structure of a building utilizing a ridge vent. Such vents are created by an open slot running along the roof ridge, which causes ventilation out of the attic by convection air flow and by suction from wind blowing across the roof. A strip of air permeable material is installed over the ridge slot which prevents the ingress of moisture and debris, but allows air flow for ventilation. A ridge cap is then installed over the air permeable strip.
For roofs having contoured shapes, such as roofs having an outer surface formed by a roofing panel having a plurality of stiffening ribs and standing seams, it is known to use a ventilation strip having a surface which includes a plurality of recesses shaped to match the ribs or standing seams of the roof panel. The strip has an air-permeable portion in order to allow airflow. A ridge cap is then installed over the air-permeable strip. Such a system is described in U.S. Pat. No. 5,561,953, which was invented by the present inventor.
A problem has been identified, however, which arises during the installation of a ridge cap over the ventilation strips. The problem is based upon crushing of the air permeable strip in the fastener connection area and/or dimpling or pull through of the fastener due to overdriving. The problem does not exist for some styles of roofs in which fasteners can be installed on or near stiffening ribs. However, when fastening occurs away from a stiffening rib, through the ridge cap, the ventilation strip and into the decking, the ventilation strip can be locally crushed during fastener installation, resulting in an uneven or damaged ridge cap. This problem is further evidenced in roof vent material having greater thicknesses, such as two or more inches, which is starting to see use in profiled ridge vent applications for metal and/or composition roofs. This can lead to a further problem of creating an entry point for moisture through the ridge cap and into the sheathing and internal roof support structure.